Is there any advantage or disadvantage to running my antenna cables
(mostly RG-8 and some RG-58 and Twinax for loops) in metallic
electrical conduit, probably 1/2" EMT?

The shack is in the basement and various antennas come in through the
roof/attic, three stories up. Currently the antenna cables drop down a
fairly clear hole shared with some vent pipes and Ethernet (CAT-5) and
phone wires.

I have some 1/2" EMT with the tools and some experience
bending/installing it.

I do observe some RFI between computers etc. throughout the house and
the ham/SW antennas. Would putting either the coax or the CAT-5 or both
(separate conduit) help any?

I'm guessing the antenna and ethernet conduits, if I do it, should be
bonded to the household ground near the electrical panel etc. for
safety. Am I likely to get any grief from the electrical inspectors by
using metallic conduit for running non-AC cables, or for bonding it to
the same grounds? To me it's a no-brainer that a common ground would
increase safety but in past electrical inspections they've given me
some minor grief for the antenna cables which were well-grounded near
the entrance panel. They pointed to a really really crappy CATV
installation and said that I had to do it that way.

Tim.